Make method not found error reporting a little more resilient

src/core.c/Exception.pm6

@@ -194,7 +194,7 @@ my class X::Method::NotFound is Exception {
         if nqp::can($!invocant.HOW, 'methods') {
             my @invocant_methods = $!invocant.^methods(:local)>>.name;
             for $!invocant.^methods(:all) -> $method_candidate {
-                my $method_name = $method_candidate.name;
+                my $method_name = (try $method_candidate.name) // '?';
                 # GH#1758 do not suggest a submethod from a parent
                 next if $method_candidate.^name eq 'Submethod' && !@invocant_methods.first($method_name, :k).defined;
                 my $dist = StrDistance.new(:before($.method), :after(~$method_name));